Neck ring for a gas cylinder



FIG. 1 is a top perspective view of a neck ring for a gas cylinder showing my new design;

FIG. 2 is a front elevational view thereof, the rear and side elevations being identical in appearance;

FIG. 3 is a top plan view thereof; and

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a neck ring for a gas cylinder, substantially as shown and described. 